The present invention relates to an improved process for obtaining juices from fresh fruits which process yields an improved, sterilized product having retained taste and aroma of the fresh fruit from which the juice was extracted.
Historically, the production of fruit juices has been achieved by processes that not only are expensive in capital equipment requirements, time and labor, but which also render the residual fruit pulp or concentrate unfit for human consumption. Further, such prior art processes generally provide a final juice product that, after pasteurization and/or sterilization has a taste distinct from the fresh fruit due to the processing conditions to which the juice product has been subjected.
By way of example of prior art processes, current commercial production of apple juice involves the steps of crushing the fruit, mixing the crushed fruit with rice hulls for better handling, and pressing of same to achieve a cloudy juice extract and a residual fruit-rice hull pulp. Due to the presence of the rice hulls, the residue or filtrant is not suitable for human ingestion, and is either discarded or utilized as animal feed. The cloudy juice extract is then prefiltered to provide a primary juice, leaving behind further quantities of fruit pulp. Prefiltered juices may then follow one of two processing routes. Depending upon the particular juice being processed, it may be desirable to treat same with one or more enzymes which break down particular pulp residual segments of the juice and lower viscosity of the juice. The juice, treated or untreated with enzymes product, may then be subjected to ultrafiltration followed by aseptic packaging. Alternatively, the pressed or prefiltered juice may be mixed with a filtering aid such as diatamaceous earth followed by filtration, through plate and frame filters, sparkling filters or the like. The final filtrate is then pasteurized and bottled hot, while the unusable filter sludge is discarded.
Following the procedures of the above processes, as noted above, overall cost is intensive, both from a capital investment standpoint and from an operational standpoint. For example, the various filters require frequent maintenance and/or cleaning, particularly the plate/frame filters. Also microorganisms collect in the filter media and can contaminate juices from subsequent filter passes.
The prior art, even in use of ultrafiltration devices, has found it necessary to first crush the fruit and mix the fruit with rice hulls, and also to prefilter the crushed fruit prior to ultrafiltration. In other words, while ultrafiltration has heretofore been generally utilized for the extraction of various plant juices, the plants have been first pressed and prefiltered, just like other prior art filtration processes. Such ultrafiltration systems, however, still have generally encountered severe membrane fouling due to suspended solids and/or concentration effects as a result of recirculation.
One such prior art process involving the use of ultrafiltration is disclosed in U.S. Pat. No. 4,551,341 to Blanie et al. Blanie et al. is directed to a process for producing clear plant juices in which, following a conventional pressing step, the pulp is separated from a primary juice. The primary juice is then adjusted for pH within a range between 3.5 and 4.0 and for temperature within a range of 50 to 65 degrees centigrade and subjected to a first stage of ultrafiltration to separate primary juice from pectate raw concentrate. The raw concentrate is then passed to at least a second stage of ultrafiltration after being diluted, if needed, with water or clear juice. Blanie et al. discloses ultrafiltration to exclude products having a molecular weight above 15,000 to 25,000 and preferably operates at an introduction pressure within a range of 3 to 5 kilograms per square centimeter and an exit pressure in a range of 1 to 2 kilograms per square centimeter. Tubular ultrafiltration membranes are stated to be preferred by Blanie et al. as permitting a greater linear speed of circulation of fluids and a reduction in the risk of clogging of the membrane. While maximum temperatures of 65 degrees Centigrade are stated to be usable with a number of commercially available membranes, temperature constraints are stated to tend to disappear with the utilization of metallic materials or other porous materials having a predetermined porosity to the ultrafiltration.
In addition to Blanie et al., additional prior art known to exist includes U.S. Pat. Nos. 2,079,542 to Bauer et al.; 2,724,652 to Brent et al.; 3,042,528 to Rowse; 3,053,668 to Lund; 3,301,684 to Bosg; and 3,346,392 to Lowe et al., each of which is directed to production of fruit and vegetable juices following conventional prior process set forth above.
The present invention is directed to an improved process for the production of fruit juices, involving ultrafiltration, but where it is necessary to only process the fruit to a pumpable fluid puree state, add liquefaction enzymes, if necessary, and thereafter pump the resulting puree of fruit and juice directly through an ultrafiltration system that is defined by a rigid porous housing having a food grade ultrafiltration membrane secured along inside walls of the housing. There is no known prior art that is believed to anticipate or suggest the process of the present invention.